The role of peripheral vision in visually guided behavior is being investigated with emphasis on the differences between recognition (focal vision) and orientation (ambient) functions. These studies include analysis of physical parameters such as optical quality, spatial frequency, field location and size, the influence of psychological and physiological stress on the orientation function of the peripheral fields and the interaction among peripheral vision, the vestibular, and somatosensory systems as determiners of spatial orientation. A possible advantage of visual narrowing by reduction of reaction time in the central narrowed field is under investigation. The nature of visual narrowing under stress will be studied to determine whether it represents a true loss of sensitivity or represents a change in response criterion. An objective of these studies is to develop quantitative techniques for the evaluation of peripheral function both as a supplement to classical clinical perimetry and with respect to human engineering and perceptual-motor skill activities. Methods for the amelioration of disorientation resulting from a mismatch, as compared with the past experiences of the organism, among the sensory systems involved in spatial orientation are also under investigation.